McCulloch Chain Saws

[belgian]

Roland, it should, you may have to mix and match the AV fittings, the older versions had a CP type AV.

Thanks Randy, a quick look at the IPL tells me that it should work, but you never know with the different version macs. It's a nice project for when I have some more time....kinda busy right now !

 

[cbfarmall]

Here's 2 Macs that showed up today. One very nice Super 250 (yes, an ebay saw, definitely worth it) and a very decent 740 that's supposed to fire--they both certainly have good compression. The S250 has great spark and I got it to fire on the first pull with a bit of priming. The sprocket has almost no wear and judging by the condition of the rest of the saw, is original. The Mac9 flatback is dated '73. Airbox is super clean. All in all a beautiful saw. As far as the 740 goes, besides some TLC and a carb kit, all it seems to need is the screw for the flywheel cover. Does anyone here have one?

Chris B.

 

[Brian13]

Very nice Chris. They both look clean. That Super 250 looks like it has seen hardly any use.

 

[CM76]

Here's 2 Macs that showed up today. One very nice Super 250 (yes, an ebay saw, definitely worth it) and a very decent 740 that's supposed to fire--they both certainly have good compression. The S250 has great spark and I got it to fire on the first pull with a bit of priming. The sprocket has almost no wear and judging by the condition of the rest of the saw, is original. The Mac9 flatback is dated '73. Airbox is super clean. All in all a beautiful saw. As far as the 740 goes, besides some TLC and a carb kit, all it seems to need is the screw for the flywheel cover. Does anyone here have one?

Chris B.

Very nice saws Chris. That Super 250 is a superb original example of the breed. The big old 740 looks good as well. I am sure someone here will have a spare flywheel guard (55615) and the grill for the airbox cover (55659) to finish the saw off. I have a number of saws which are missing the rear grill - it seems to become distorted easily, and pops out in the middle. I have to chase up some as well.

Congrats on these two - they are a great find.

Regards,

Chris.

 

[ric5141]

Chris that 250 is a sweet looking saw.....

Congratulations!

 

[leeha]

Here's 2 Macs that showed up today. One very nice Super 250 (yes, an ebay saw, definitely worth it) and a very decent 740 that's supposed to fire--they both certainly have good compression. The S250 has great spark and I got it to fire on the first pull with a bit of priming. The sprocket has almost no wear and judging by the condition of the rest of the saw, is original. The Mac9 flatback is dated '73. Airbox is super clean. All in all a beautiful saw. As far as the 740 goes, besides some TLC and a carb kit, all it seems to need is the screw for the flywheel cover. Does anyone here have one?

Chris B.

You got yourself a couple nice sweeties there Chris.
The S250 is super clean. Congrats on 2 nice saws.


Lee

 

[cbfarmall]

Thanks guys. I knew the S250 was nice when I bid on it, but looking closer at the saw I've noticed: the bar studs still have cadmium plating and the bar nuts still have fresh galvanized coating, all the gaskets (at least, what I can see) are still the original coloring and not yet stained from oil/gas/dirt, the bolts on the flywheel cover and elsewhere don't look as if they've ever been turned, the model tag is still fastened to the oil tank, the muffler is still the original black and not yet oxidizing.

Sometimes you get lucky. The 740 is pretty darned nice, too.

Chris B.

 

[heimannm]

how many different size flatbacks are there and what models do they cover ? i see parts for sale that look like mine but even with my carb number sellers don't seem to know what they fit.

As far as I know, there was only one size McCulloch flat back carburetor used on chain saws. All the different models had a throttle bore of .812 and a venturi of .687.

PN 84050 (MAC 6) had a choke and was used on the Super 250 and Super 550 only.

PN 84260 (MAC 1) had the primer and an idle speed governor, and high speed (air vane) governor and were used on gear drive saws (800 Series) and the 740 and 790. 795's and some 797's had the large flat back with no idle speed governor and no high speed (air vane) governor.

There are perhaps at least two more; one with a primer and no idle speed governor and one with a primer and a provision for the high speed (air vane) governer and no idle speed governor on the throttle shaft but it is not listed in my McCulloch carburetor book. The number stamped on the carburetor is not the same as the part numbers McCulloch used to I.D. the carburetors...go figure. As with everything McCUlloch, there were exceptions to all the rules as well.

The kart carburetors were all described as model BDC (2, 4, 14, etc.) and were quite different even though the fuel pump diaphragm and gaskets were the same. The metering diaphragm has some additional holes that don't work in all the saw carburetors.

Mark

 

[tomdcoker]

from what it sounds like you have a flatback carb. the forward port of the primer has a check valve in the carb body. i think you can use the rubber metering needle seat out of a tillitson Hl as a substitute seat for the check valve.
also you may find some thick wall fuel line that fits the hole and razor slice a short piece off to fit.

I used a piece of fuel line tubing and got it repaired. Thanks for the information. Tom

 

[tomdcoker]

There is a post in the McCulloch Carburetor thread (see link below) where Stinkbait shows that the rubber seat from a Tillotson HL carburetor can be used to replace the original rubber seat for the check valve in the primer on the big McCulloch Flat Back carburetor.

The information about using the Homelite duck bill as a replacement check valve is for the 10 Series carburetor. I have not gotten around to putting together the 10 Series carburetor thread yet.

Mark

Thanks for the information and link. I used a piece of tubing and have that part repaired. Now I am waiting on the repair kit. Thanks again. Tom
P S I read the tutorial on your link about rebuilding the Mac carbs. and learned a lot. Thanks for the link. Tom

 

[cpr]

Will a clutch drum from a SP80 fit a Super 250? Tomorrow, I'll show you why I'm asking such an oddball question...

 

[heimannm]

Will a clutch drum from a SP80 fit a Super 250? Tomorrow, I'll show you why I'm asking such an oddball question...

No, the clutch drum for the Super 250 is smaller diameter but wider and a large diameter shaft. The SP80/81 had a unique size,different even from the rest of the 10 Series and 600 Series, which by the way are exactly the same. I don't know about the shaft diameter and taper on the 80/81 compared to the 10 Series/600 Series but I do know the drums are different.

The clutch drum is the same on all of the large frame (direct drive) saws, from the D-30 all the say through the SP125 including the Super 250.

Mark

 

[Brmorgan]

Look in the 'webbed' section of the left side of the rear handle brace on those saws. There is a long, thin flat 'pad' where the serial # should be. Should see "77-1234" or something like that. The "77" in my example would mean it the saw is Mac 77. My Mac77 looks similar to the saw with the "X" shaped sight glass on its gearcase. I think that saw may be a 49 or a 77. I think the other saw is a 4-30, or something similar. The Homelite experts here will know for sure.

I could sure use the front bar stud and the bumper spike from the saw with the "X" sight glass. Let me know if you wanna part it out. The stud is held on by one nut (backside of the bumper spike). I believe it either pulls out or threads out after the nut is removed.

The mystery part is some sort of auger or brushcutter gearbox attachment I believe. Made to fit one of the Mac saws such as a 33/35/39. I could easily be wrong however...

For sure you can have a bar stud and the spikes. I just want to trace the spikes out on some quad graph paper first so I have the pattern for future reference. I have the day off work tomorrow so I'll try to remember to get 'round to pulling that stuff off for ya. Pretty sure I won't be making a runner out of this one, so if there's anything else you want/need off of it, let me know.

If it IS a 77, are major parts worth much? As I said, this one isn't seized so the topend may be good, who knows. Hopefully I can get a bit dirty tomorrow and find out.

 

[Eccentric]

Here's 2 Macs that showed up today. One very nice Super 250 (yes, an ebay saw, definitely worth it) and a very decent 740 that's supposed to fire--they both certainly have good compression. The S250 has great spark and I got it to fire on the first pull with a bit of priming. The sprocket has almost no wear and judging by the condition of the rest of the saw, is original. The Mac9 flatback is dated '73. Airbox is super clean. All in all a beautiful saw. As far as the 740 goes, besides some TLC and a carb kit, all it seems to need is the screw for the flywheel cover. Does anyone here have one?

Chris B.

Thanks guys. I knew the S250 was nice when I bid on it, but looking closer at the saw I've noticed: the bar studs still have cadmium plating and the bar nuts still have fresh galvanized coating, all the gaskets (at least, what I can see) are still the original coloring and not yet stained from oil/gas/dirt, the bolts on the flywheel cover and elsewhere don't look as if they've ever been turned, the model tag is still fastened to the oil tank, the muffler is still the original black and not yet oxidizing.

Sometimes you get lucky. The 740 is pretty darned nice, too.

Chris B.

You're killing me Chris. I was watching that Super 250 auction. Couldn't swing it right now. Glad that you got it, and that it was a clean as it looked. Post some video of it running!

For sure you can have a bar stud and the spikes. I just want to trace the spikes out on some quad graph paper first so I have the pattern for future reference. I have the day off work tomorrow so I'll try to remember to get 'round to pulling that stuff off for ya. Pretty sure I won't be making a runner out of this one, so if there's anything else you want/need off of it, let me know.

If it IS a 77, are major parts worth much? As I said, this one isn't seized so the topend may be good, who knows. Hopefully I can get a bit dirty tomorrow and find out.

Thanks a bunch my friend. I don't think it's a 77, as the carburetor setup (what there is of it on your saw) looks different than what's on my 77. Muffler is different too. More than likely it's a 4-30 or a 49 or some other model. The Mac experts here are more knowledgeable than me on these saws though. Hopefuly they'll chime in if I'm off base.

I'll have to look to see what else I need. Thanks again. Gotta go to work now...

 

[cbfarmall]

Glad that you got it, and that it was a clean as it looked. Post some video of it running!

Till I get my carby kit, you'll have to be content with these shots of the saw and a 20" roller nose I dug out of my stash. Wasn't meant for this saw, but a bit of filing made it fit like a glove.

Chris B.

 

[cbfarmall]

PN 84050 (MAC 6) had a choke and was used on the Super 250 and Super 550 only.

Mark,

My Super 250 has a Mac9.

Chris B.

 

[lawnmowertech37]

Mark,

My Super 250 has a Mac9.

Chris B.

Chris that is a flat back mac carb

 

[cbfarmall]

Chris that is a flat back mac carb

I realize that. I was putting it up for the benefit of Mark's little list.

Chris B.

 

[Brmorgan]

Thanks a bunch my friend. I don't think it's a 77, as the carburetor setup (what there is of it on your saw) looks different than what's on my 77. Muffler is different too. More than likely it's a 4-30 or a 49 or some other model. The Mac experts here are more knowledgeable than me on these saws though. Hopefuly they'll chime in if I'm off base.

I'll have to look to see what else I need. Thanks again. Gotta go to work now...

The saw with the muffler and flywheel etc. still on it says it's a 3-25 on the tag. The other one with the X on the gearcase has no tag anywhere on it, so after I pulled the stud and spikes for you from it, I pulled the topend off and measured. It's 63.5mm, so it's either a 73 or 77, I think? I got the piston free in the cylinder but I can't pull it out yet; it binds up once it gets below the exhaust. I had to use the old grease gun trick to pop the piston loose, and just unbolted the bottom end of the rod to get it free. I think I bent the rod in the vise trying to twist the piston out of the jug though. If I ever do manage to get it free, the topend does look perfectly usable if a guy had some new rings.

 

[cpr]

Thanks for the answer Mark. Here's why I asked. I need a new drive sprocket for the Super 250. I bought what I thought was a rim and drum based on the photos when THIS arrived. Only McCulloch, God love 'em, could have designed, manufactured, packaged, and sold this thing. I refuse to run it, partly because it's rediculous, partly because I think it's better as a minty original, odd-ball part. I'm keeping it and laminating the directions and shims.

Hilarious...